Clown fish itching?

It looks like my two clown fish are itching themselves on rocks. To me that doesn't seem good but at the same time of this possible "itch" they're nipping at the rocks. Is there a problem other than possibly being hungry?

Current water params:
Ammonia: 0
Nitrate: 40 ppm
Nitrite: 0 ppm
pH: 8.4

 

your nitrates i think is a bit high. when was the last time you did a water change?

 

I did 20 gallons last Saturday, and the nitrates dropped a little. I know in order to drop nitrates the best answer is water changes. I'm just wondering if it's starting to affect my fish or if there something else I should check that may also high

 

do you have a fowlr? how long have you had the tank set up? how long have you had the clowns?

 

Yes FOWLR. I've tank was set up in Sept. '10 and clown fish went in second week of Oct. '10. Moved my tank three blocks over on January 8th. Took about an hour and a half

 

do you see any visible white spots? are they breathing heavily? could be a sign of ich.

 

No white spots. As far as the breathing.... not sure

 

Sounds to me like they are getting ready to spawn. They will nip at the rock to make a good spot to lay. And the itching could be part of their little dance.